Desktop apps and web apps are very different beasts.
I would agree web sites that need to offer a few forms are quite different from computer applications. Desktop apps and web apps, in contrast, differ only in the underlying infrastructure, of deployment, and efficiency optimization issues.
Bear Bibeault wrote: GWT tries to bring the desktop programming metaphor to the web, and it's perfectly appropriate for some uses, but that metaphor just isn't going to go much of anywhere in the grand scheme of things -- it's just not very suitable to the purpose, and not even in the mindshare of up-and-coming web devs. They didn't "grow up" writing Windows or X desktop apps like we did, and telling them they need to write the structure of UI in a programmatic manner in Java rather than in a declarative manner is likely to get you some odd looks.
Exactly, just like the mainframe programmers who didn't grow up writing Java or even Pascal, and who would give you odd looks if you told them they should start doing, say, test-driven development.